Cream 1/2 cup - 75 mL of butter and 1/2 cup - 75 mL sugar until light and fluffy; add egg and beat well.
Blend in 2 cups - 500 mL flour, sifted with baking powder and salt, alternating with milk.
Spread batter in greased 9x9x2-inch pan. Cover with blueberries.
Blend cinnamon with remaining sugar, flour and butter until crumbly. Sprinkle mixture over blueberries.
Bake at 375 degrees F - 190 degrees C for about 45 minutes or until done.